Shell South Uist SERPENT final report

This report presents the results from the SERPENT project collaborative research with Shell at the South Uist deep-water exploration oil well, drilled from the Leiv Eiriksson semisubmersible rig in the Faroe- Shetland Channel. The study was designed to investigate seabed disturbance resulting from the drilling activities at South Uist and the effects of these activities on the benthic environment and megafaunal organisms. The remotely operated vehicle (ROV) was used to take video transects of at least 100m in length from which the extent of drill cuttings and megafaunal densities were assessed. Cuttings were clearly visible on the seabed and were over a metre deep close to the well with a shallower layer extending to beyond 100m to the west. Twenty-five megafaunal taxa from seven phyla were observed at South Uist and species density and diversity were reduced close to the well. In addition sediment samples for subsequent chemical analysis were collected at 25, 50, 75 and 100m from the well and specimen samples of the characteristic megafauna were obtained.